Find the equation of the circle with centre at origin and radius $4$

Find the centre and radius of the circle $x^2+y^{2 }=25$

Find the centre and radius of the circle.

$(x-5{)}^{2 }+(y-3{)}^2 = 20$

Find the centre and radius of the circle.

${\left(x-\frac{1}{2}\right)}^2 +{\left(y+\frac{1}{3}\right)}^2 =\frac{1}{36}$